1. Field of the Invention
The present invention relates to management of projection data, such as raw data generated in modality, and more particularly to a data managing system that manages raw data generated in an X-ray computed tomographic apparatus (hereinafter, referred to as the X-ray CT apparatus), an X-ray CT apparatus, and an X-ray CT system.
2. Description of the Related Art
In the field of medical imaging, there are various kinds of modality, including X-rays, ultrasound, CT, magnetic resonance imaging (MRI), and nuclear medicine, and each provides useful images as clinical information. Recently, together with the advancement in the respective kinds of modality, improvements in image processing techniques, speedups in computer operations, and enhancement in resolution have made it possible to produce an image of an internal structure of a human body more accurately in various forms. Meanwhile, a size of data to be handled has increased, and a major portion of the CPU operations is occupied by image processing or the like, which raises a problem that a following photographing work cannot be started until the image reconstruction is completed. Also, there is another problem that when a vast volume of data (raw data, projection data, etc.) obtained through photographing is recorded in a hard disc (hereinafter, abbreviated to HD) provided in advance to the respective kinds of modality, the recording work takes so long that efficiency of a diagnostic work is decreased. Further, because a data size of the raw data is generally larger than that of a reconstructed tomographic image while the equipped HD is also used to store various kinds of data, such as patient information and diagnostic images in the past, there arises still another problem that the HD is not large enough to record a huge volume of raw data.
Hereinafter, an X-ray CT apparatus will be described by way of example in order to explain these problems more concretely. The X-ray CT apparatus generates raw data by scanning a subject with exposure of an X-ray. The raw data thus generated is sequentially recorded and saved in an internal HD of the X-ray CT apparatus or a certain storage medium. An X-ray CT image can be obtained by reading out the raw data for reconstruction followed by certain image processing. However, because the HD stores many items of examination data, such as CT image data and patient information, in addition to the raw data, the HD is not able to save a huge volume of raw data. Moreover, when image reconstruction is performed subsequently to raw data generation, a major portion of the CPU operations is occupied by the image reconstruction processing and a following photographing work cannot be started.
In addition, a multi-slice X-ray CT apparatus has been becoming popular in recent years, through the use of which image acquisition with high accuracy within a wide range can be achieved in a short time by irradiating a cone-shaped X-ray beam to a subject and detecting X-rays having passed through the subject in a multi-array detector. When compared with a single-slice X-ray CT apparatus, photographing by the multi-slice X-ray CT apparatus generates a far larger volume of raw data, and the problems described above become more apparent.
For example, in the case of raw data generated in a multi-slice X-ray CT apparatus having a 16-array detector, a full storage capacity of a typical disc with a 4.8-GB capacity is 70 rotations at the scanning rate of 0.5 sec. on one side of an MO. However, because the maximum size of the raw data generated in the multi-slice X-ray CT apparatus having the 16-array detector is 6.4 GB, the capacity of the internal HD of the apparatus is by no means sufficient. Also, not only recording takes 30 min. or longer, but also image reconstruction requires a considerable time, which may possibly cause a decrease in the efficiency of a diagnostic work.